1. Field of the Invention
The present invention relates to a file system, for which a large memory capacity recording medium, such as a hard disk, is provided which enables the restoration of a defective file generated due to an accident occurred during the recording of data, and to file management apparatus incorporated therein.
2. Related Background Arts
Heretofore, file systems incorporating hard disks have been used mainly as external storage media for computers. A file system employed for this purpose must write and read data with high reliability, and it is assumed that such a file system should normally finish a data recording operation in progress when a stoppage, such as a power loss, occurs. Thus, a function is provided for a file system for monitoring the power supply voltage, and for supplying power when the voltage is reduced, so that even if there is a sudden, complete loss of power, auxiliary power can be supplied for a short period of time to permit the data recording operation to be finished normally. Alternatively, two file allocation tables (FATs) may be provided for a file system and used for disk file management, so that following the occurrence of a stoppage, a defective file can be detected by comparing the two FATs. A file management process is thus required for a plurality of FATs.
Further, since the costs of manufacturing a large memory capacity recording media such as hard disks have been dramatically reduced, a video recorder incorporating the hard disk for recording video and sound data have been developed. Unlike computer data, the recording of video and sound data requires extremely large amounts of memory media; however, with the reduction in the costs associated with the manufacture of hard disks, as a recording media employed for a video recorder installed in homes, hard disks are gradually replacing video tapes.
A video recorder having built-in hard disk uses the MPEG2 method to encode and compress video and sound data, and records the resultant data on a recording medium, the hard disk. During reproduction, the recorded data is read from the hard disk, and a decoder converts that data into the original video or sound data, which is then output. Unlike video tape, a hard disk can be accessed randomly and can both reproduce and record data at the same time, so that video recorders having built-in hard disks are assumed to have a favorable future as home video recorders. In addition to video recorders, in consonance with the growth in popularity of broadband, the wide use of recording/reproduction apparatuses having built-in hard disks, for recording video and sound data, appears promising.
For a file system, such as a hard disk recorder, a function is required to prevent the abnormal termination of a recording operation due to a power cutoff and to avoid the production of a defective file. However, it is not preferable for, as with a file system used for a conventional computer system, a power monitoring device and a battery, or a plurality of FATS to be provided to cope with a stoppage because system manufacturing costs would be increased. While the reliability required for the recording and reproduction of video and sound data need not be as high as that required for computer data, for a file system cost reduction is a more important problem.